Process for producing fluorocarbons



Patented Feb. 12, 1952 PROCESS FOR PRODUCING FLUOROCARBONS Robert D. Fowler, William B. Burford, III, and Harry G. Anderson, Baltimore, Md., assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application November 25, 1946, Serial No. 712,038

6 Claims.

The present invention relates to a process for producing fluorocarbons and, more particularly, to a process for preparing fluorocarbons from hydrocarbons of relatively high molecular weight.

Highly fluorinated hydrocarbons, especially completely fluorinated hydrocarbons and hydrocarbons having not more than one to three unsubstituted hydrogens, are particularly valuable for use as lubricating oils in processes where it is desirable to provide inert lubricants. It has recently been found that hydrocarbons may be highly fiuorinated by passing vapors of said hydrocarbons into contact with fluorides of certain metals, such as cobalt, manganese and silver, in a higher valence state at temperatures between 150 C. and 400 C. Although such processes in general produce high yields in the case of the low molecular weight hydrocarbons (say, up to heptane), disappointing results have been obta ned by the application of these processes to hydrocarbons of high molecular weight, say, of the order of about 17 to about 23 carbon atoms per molecule. Moreover, the high temperatures employed tend to produce a higher proportion of sci sion and fluorinolysis products than is desirable.

It is an ob ect of the present invention to provide a simple and inexpensive process for producing fluorocarbons of relatively high molecular weight in high yield.

It is another object of this invention to provide a relatively low temperature fluorinating process for hydrocarbons which produces a fluorocarbon product with relative y low production of scission and fluorinolysis products.

bons of relatively high molecular weight, such as those having about 1'7 to about 23 carbon atoms per molecule, preferably those boiling between about 250 C. and about 400 C., it is also appl cable to the fluorination of hydrocarbons of lower or of higher carbon content, including those having about 6 to about 30 carbons. Certain other substances, such as halogenated hydrocarbons, Vaseline, and phenol resin, may

also be fiuorinated by the method of the present invention. The term "hydrocarbon may be understood to include hydrocarbons of the paraffinic, olefinic, aromatic and naphthenic series.

The bismuth pentafluoride is preferably in comminuted form and may be prepared by fluorination of bismuth trifiuoride with elemental fluorine.

The range of temperatures employed varies somewhat with the particular hydrocarbon to be fluorinated but, in general, the reaction temperature in the present process is lower than that emp oyed in fluorination with certain other metal fluorides, such as cobalt trifiuoride and manganese trifiuoride. Bismuth pentafluoride is so drastic a fiuorinating agent that, once the reaction has started, it is desirable to control the temperature to prevent degradation of the product. Such control may be effected by provision of cooling means. In vapor'phase reaction the temperature must be somewhat above the boiling point of the feed stock at the start of the reaction, and may have to be increa ed as much as -200 C. to complete the reaction. although, because of the greater reactivity of BiFs, such increases will be much smaller than the corresponding values for the other fluorinating agents.

One of the great advantages in the use of bismuth pentafluoride is its effectiveness as a fluorinating agent in liquid phase reaction. Due to the powerful fiuorinating character of bismuth pentafluoride when used to fiuorina e hydrocarbons, various types of fluorocarbons, formerly either difiicult or impossible to produce with the fiuorinating agents of the prior art, may be produced when employing bismuth pentafluoride at relatively low temperatures. Thus, the use of bismuth pentafluoride in the liquid phase results in the fluorination of long chain or high molecular weight compounds to a high degree of completion, whereas more drastic methods, especially temperaturewise, with other fluorinatine agents are incapable of producing the desired products without relatively high lo s through scission and fluorinolysis. Better yields of fluorocarbons are thus produced by the process of this invention than have formerly been found possible when fluorinating these materials.

In carrying out the reaction in the vapor phase, it is preferred to have the bismuth pentafluoride in a rotary reaction cylinder equipped with agitator blades and to pass the hydrocarbon to be fluorinated in vapor phase in intimate contact With the bismuth pentafluoride therein. The

bismuth pentafluoride may only partially occupy the volume of the cylinder or may fill the same substantially entirely. If desired, an inert gas, such asnitrogen or a vaporized fluorinated hy drocarbon (usually of low molecular weight), may be employed as a diluent gas and may be passed into. the reaction cylinder in admixture with the vaporized hydrocarbon. A slow rotation of the cylinder is preferably provided for obviating channelling of the bismuth pentafluoride' upon the introduction of the gaseous hydrocarbon.

Thefluorination of bismuth trifluoride to form bismuth pentafluoride is carried out at high temperatures, of the order of approximately 450 C., by contacting the bismuth trifluoride with elemental fluorine. The reaction may be brought about in a high pressure autoclave, or, if carried out in a reactor similar to that employed for the vapor phase fluorination described in the preceding paragraph, condensing means are provided for rapid reduction of the temperature of the eflluent gases, as bismuth pentafluoride has a high sublimation pressure at the temperature of its formation.

Upon'completion of the vapor phase fluorination reaction described, the vaporized fluorocarbon and the hydrogen fluoride formed in the reaction are removed from the reaction chamber together and are condensed in a cooling chamber. Two liquid phases are formed, and these may be separated by settling, decantation and/ or centrifugation. -Thereafter, each layer may be separately purified by fractional distillation or fractional condensation, or, if desired, the origi- 1.;

nal vapors as removed from the reaction chamber may be fractionally condensed.

The process may be carried out in batch or in continuous operation, as well as in an intermittent operation. Thus, vaporized hydrocarbons may be passed into contact with bismuth pentafluoride in areaction vessel, which is thereafter closed and heated to the reaction temperature, the products of the reaction being withdrawn after a suitable time period. Again, while not preferredthe hydrocarbons may be continuously passed through a reaction cylinder of suitable length in countercurrent flow with respect to a moving'bed of bismuth pentafluoride. The reaction may be carried out at atmospheric, superatmospheric or reduced pressures.

In carrying out the fluorination of hydrocarbons in the liquid phase, low temperatures are employed for hydrocarbons of about l? to about 23 carbon atoms per molecule and for the long, chain and polymeric hydrocarbons and hydrocarbon derivatives for which the present invention is so well adapted.

As noted supra, fluorocarbon solvents may be employed as reaction media, and those found particularly suitable for carrying out the present process are the highly ,fluorinated carboncompounds boiling about 180 C. and which are fluid at the, reaction temperatures. 7

The fluorocarbon solvent may contain, a small proportion of elements other than carbon and fluorine. Thus, compounds containing one or two atoms of residual hydrogen in, the molecule maybe used, especially as part of this hydrogen is usually replaced by fluorine during the process. The character of this side reaction is generally not sufficiently energetic to affect the main reaction or to interfere seriously with its control. Likewise, small proportions of other elements such as chlorine, bromine, oxygen or nitrogen may be present in the molecule without materially affecting the predominantly fluorocarbon character of the solvent.

A- proportion of the desired fluorination products themselves may also be employed as fluorocarbon solvents, their use having the advantage that the introduction of foreign materials is thereby avoided. The process may be carried out in cyclic manner, with a part of the product of each fiuorination being returned to the next successive fluorination for useas a fluorocarbon solvent therein.

As in the vapor phase operation, the liquid phase procedure may also be carried out in batch, intermittent, or continuous operation. Good agitation promotes uniform reaction and prevents local, over-heating thus facilitating temperature control. In batch operation, the gradual addition of the hydrocarbon to a mixture of the solvent and the bismuth pentafluoride permits a lower ratio of solvent to total hydrocarbon. This ratio may, in general, vary between about four parts of weight of fluorocarbon solvent to one part of hydrocarbon and about thirty parts to one. Cooling means may be provided for maintaining the temperature below the point where disadvantageous formation of scission and fluorinolysis products results. 7 v V The following examples are illustrative of the present invention, but it will be understood that the invention is not limited thereto:

Example of about 225 and the efliuent gases are passed through a water-cooled container where the product and hydrogen fluoride are condensed. The liquid thus formed separates into two layers, the lower of which comprises the large portion of the fluorinated oil, containing some hydrogen fluoride. The fluorinated product is obtained in purified form by fractional distillation, and is found to have a boiling range from about -290 C.

Example 2 About 50 parts by weight of a lubricating oil having an average molecular weight of approximately 328-and having 95% boiling over 300 C., is mixed with 1000 parts of a fiuorinated kerosene fraction in a nickel reaction vessel, and the mixture is agitated, during the gradual addition of 800 parts of bismuthpentafluoride over a fourhour period. The temperature is raised to, and maintained at about 10050. for an additional four hours.

It is then allowed to cool to room temperature, and the product is remoi' ed, the fluorinating agent is filtered off and the filtrate is subjected to fractionaldistillation to recover the fluorocarbon product. The product obtained has a boiling range of from 180 C. at 1 atmosphere to 250 C. at 10 mm.,' and a yield of approximately 30% to 60% of the calculated theoretical yield is obtained. 7 V

Although the present invention has been described with reference to specific embodiments and examples, it will be appreciated that variations and modifications thereof may be made and that equivalents may be substituted therein with out departing from the spirit of this invention. Such variations and modifications are believed to be within the scope of the present invention and within the purview of the appended claims.

We claim:

1. A process for substantially completely replacing with fluorine the hydrogen atoms of a petroleum lubricating oil consisting of hydrocarbons having from about 17 to about 23 carbon atoms per molecule and having a boiling range between about 250 C. and about 400 C. with a relatively low production of scission and fluorinolysis products which comprises heating said petroleum lubricating oil with bismuth pentafluoride as the sole fluorinating agent in a temperature range running from 90 C. to 450 C., and then separating the hydrogen fluoride produced from the substantially completely fluorinated lubricating oil.

2. A process as defined in claim 1 wherein vapors of said lubricating oil are passed over a bed of bismuth pentafluoride in a temperature range lying between the upper limit of the boiling range of said lubricating oil and 450 C.

3. A process as defined in claim 2 wherein said lubricating. oil has an average molecular weight of approximately 240 and the bed of bismuth pentafluoride is maintained at a temperature of about 225 C.

4. A process for substantially completely replacing with fluorine the hydrogen atoms of a petroleum lubricating oil consisting of hydrocarbons having from about 17 to about 23 carbon atoms. per molecule and having a boiling range between about 250 C. and about 400 C.

with a relatively low production of scission and fluorinolysis products whichcomprises heating and agitating said petroleum lubricating oil diluted with from 4 to 30 times its weight of a fluorocarbon solvent boiling between about 105 C. and about 200 C. in liquid phase contact with bismuth pentafluoride as the sole fluorinating agent at a temperature of 100 (3., separating the bismuth fluoride from the organic fluorination product by filtration, and then subjecting the organic fluorination product to fractional distillation to recover a substantially completely fluorinated lubricating oil therefrom.

5. A process as defined in claim 4 wherein said lubricating oil has an average molecular weight of approximately 328 and is diluted with 20 times its weight of said fluorocarbon solvent and said fluorocarbon solvent is a fluorinated kerosene fraction.

6. A process as defined in claim 4 wherein the bismuth pentafluoride is added gradually to the mixture of said lubricating oil with said fluorocarbon solvent.

ROBERT D. FOWLER. WILLIAM vB. BURFORD, III. HARRY C. ANDERSONx REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Wartenberg: Zeit. fur Anorgan. und Allgemeine Chem., vol. 244, 337-346 (1940). 

1. A PROCESS FOR SUBSTANTIALLY COMPLETELY REPLACING WITH FLUORINE THE HYDROGEN ATOMS OF A PETROLEUM LUBRICATING OIL CONSISTING OF HYDROCARBONS HAVING FROM ABOUT 17 TO ABOUT 23 CARBON ATOMS PER MOLECULE AND HAVING A BOILING RANGE BETWEEN ABOUT 250* C. AND ABOUT 400* C. WITH A RELATIVELY LOW PRODUCTION OF SCISSION AND FLUORINOLYSIS PRODUCTS WHICH COMPRISES HEATING SAID PETROLEUM LUBRICATING OIL WITH BISMUTH PENTAFLUORIDE AS THE SOLE FLUORINATING AGENT IN A TEMPERATURE RANGE RUNNING FROM 90* C. TO 450* C., AND THEN SEPARATING THE HYDROGEN FLUORIDE PRODUCED FROM THE SUBSTANTIALLY COMPLETELY FLUORINATED LUBRICATING OIL. 